GIS-driven insights into seasonal water quality shifts: The Ganga River’s journey through Patna’s urban drains (Bihar, India)

The Ganga River is not only the lifeline for millions in northern India, providing essential water for agriculture, domestic use, and industry, but also holds immense cultural and ecological significance. However, rapid urbanization and unregulated waste discharge have led to escalating pollution, making it crucial to assess the river’s health and irrigation suitability. The current study intended to assess the impact of different drains on the Ganga River at Patna, India, and to evaluate the suitability of Ganga River water quality for irrigation. GIS-driven methods were employed to spatially map water quality indices and visualize pollution hotspots, providing a comprehensive spatial assessment of water quality variations along the river. Multivariate statistical techniques, including Principal Component Analysis (PCA) and Pearson Correlation Matrix (PCM), were applied to identify the sources and patterns of contamination and distinguish between geogenic and anthropogenic influences. A total of 20 samples each were collected during the summer and winter seasons of 2022 and 2023, respectively. The physicochemical parameters were examined, including alkalinity, turbidity, chloride (Cl - ), pH, electrical conductivity (EC), total dissolved solids (TDS), DO, Na + , K + , PO 4 3- , NO 3 - , SO 4 2- , Ca 2+ , and Mg 2+ . Also, the water quality index (WQI) and irrigation indices such as the Sodium Adsorption Ratio (SAR), Sodium percentage (%Na), and Kelly’s Ratio (KR) were calculated to assess the suitability of river water for agricultural use. This study provides critical scientific insight into the water quality of the Ganga River at Patna, supporting researchers and policymakers in formulating targeted, drain-specific water management strategies for the Patna stretch of the River Ganga.